Scoliosis is characterized by abnormal curvature of the spine. Scoliosis can result in abnormal curvature in the coronal plane to cause lateral curvature, abnormal curvature in the coronal plane associated with incorrect lordosis and/or kyphosis, and abnormal axial alignment of the spine to cause incorrect rotation. Scoliosis may therefore present as a tridimensional deformity of the spine.
The spine is made up of vertebrae connected by discs. Scoliosis can be associated with abnormally shaped vertebrae and abnormal intradiscal spacing. For example, the vertebrae and/or the discs may make have an abnormal wedge-shape associated with spinal curvature. Scoliosis can also be associated with abnormal relative alignment of the vertebrae, or vertebral axial rotation.
While minor scoliosis can sometimes be corrected with external braces, surgical correction involving fusion of vertebra is often required in more major cases. Such surgical procedures generally seek to restore vertebrae to a more normal alignment while providing for fusion of adjacent vertebrae. Fusion of vertebrae is typically encouraged by removal of the disc material.
Intervertebral spinal inserts can be used to provide support and maintain distance between adjacent vertebrae in cases where a patient's vertebral disc has been surgically removed. Intervertebral inserts can be used in this manner to establish or approximate normal alignment of vertebrae.
Traditional manual methods for estimating of the vertebral axial rotation in scoliosis based on X-ray images were relative imprecise. For example, the traditionally measured Cobb angle only evaluates spinal curvature in the sagittal and coronal planes. The degree of axial rotation is estimated by the positions of the spinous process or pedical shadow. The availability of high quality radiographs and specifically tailored software now enables more precise measurements of vertebral position, even in upper thoracic spine where image contrast is typically poor. Rajnics, P., et al. (2001) Computer Assisted Assessment of Spinal Sagittal Plane Radiographs. J. Spinal Disorders, 14 (2), pp. 135-42. Recently, computer-processed rotation measurements obtained from digital radiographs have enabled researchers to precisely measure the vertebral axial of rotation in scoliosis patents. Piheiro, A. P., et al. (2010) Validity and reliability of a computer method to estimate vertebral axial rotation from digital radiographs, Eur. Spine J., 19 (3), pp. 415-20; Tanure, M. C. (2010) Reliability assessment of Cobb angle measurements using manual and digital methods. Spine J., 10 (9), pp. 769-74.